1. Field of the Invention
This invention relates to a method for using a reagent composition for removing oxygen from a variety of fluids, and particularly from liquid and gaseous hydrocarbons and carbon dioxide. The method is especially useful for removing oxygen from gaseous hydrocarbon streams, light liquid hydrocarbon streams such as natural gas liquids (“NGL”), crude oil, acid-gas mixtures, carbon dioxide gas and liquid, anaerobic gas, landfill gas, geothermal gas, and the like.
2. Description of Related Art
At times oxygen is present as a contaminant in various gaseous and liquid hydrocarbon and carbon dioxide streams. In some cases, the oxygen is the result of a natural gas field that is contaminated with oxygen. Oxygen is often unintentionally introduced through processing of the gaseous hydrocarbon streams. One example of this is when a compressor is used to increase the pressure of low pressure gas, such as coal seam or landfill gas. Small amounts of air, containing oxygen, can find its way into the gas stream during the compression process.
The presence of oxygen in gaseous and liquid hydrocarbon streams such as a natural gas stream can cause various problems. The oxygen will increase the amount and rate of corrosion in pipelines as well as treatment and storage facilities. It can also interfere with further treatment of the gas stream. Particularly, the presence of oxygen will degrade amine solvents that are used to remove hydrogen sulfide from a natural gas stream. This makes it difficult to remove hydrogen sulfide from various hydrocarbon streams that also contains oxygen. Removal of hydrogen sulfide and other sulfur compounds from these streams is required to meet the stringent sulfur requirements under modern environmental laws and regulations.
In fact, many pipeline companies will discount the value of a natural gas stream that contains high levels of oxygen or may even refuse to accept natural gas streams that contain more than a certain level of oxygen. Many pipeline specifications require natural gas to contain less than 10 ppm of oxygen. The use of oxygen removal systems for gaseous hydrocarbon streams is not widespread and there is a lack of an economical way to remove low levels of oxygen from natural gas streams. In many cases, a natural gas stream that contains high amounts of oxygen may be abandoned or blended with other streams to drop the oxygen content below the required specifications for pipelines.
Gaseous and liquid hydrocarbon streams also often contain significant quantities of sulfur compounds. Various sulfur compounds that are often found in gaseous hydrocarbon streams such as natural gas streams include hydrogen sulfide, mercaptans, and dimethyidisulfide. These sulfur compounds must be removed from the hydrocarbon stream in order to meet emissions standards and pipeline requirements. However, the presence of oxygen in the gaseous stream inhibits the removal of the sulfur compounds. Therefore, there is still a need for an economical way to remove oxygen from gaseous hydrocarbon streams, especially those streams that also contain sulfur containing compounds such as hydrogen sulfide.